I’m watching 365 documentaries and writing about each one in 2014. Tweet your suggestions to @documentarysite, or send an e-mail to hmcintosh@documentarysite.com. Read more.

Note: This post may contain spoilers.

Some of the most unwatchable docs are also some of the most unwriteable. I refer not to the documentary’s quality, but to its subject and the emotional punch in the gut it delivers.

Two older examples come to mind. First are the animal slaughtering scenes in Georges Franju’s Blood of the Beasts (Le sang des bêtes, 1949). Franju’s short film juxtaposes scenes of serene suburban Paris with extended shots of animals being killed and dying, from sheep to pigs to a white horse. This film represents a documentary version of a horror film for me, which shouldn’t be surprising considering the director.

Second is the onslaught of footage found in Alain Resnais’s Night and Fog (Nuit et brouillard, 1955): the mass graves, the emaciated and naked prisoners, the “products” created with or extracted from them. The most disturbing shots are the ones that seem still but actually are motion pictures. In one the camera focuses on a man sitting still until, suddenly, he blinks. That small motion is a powerful reminder of the man’s living and suffering.

The Act of Killing falls into this almost unwriteable place for me, as it has taken me almost a month to compose this response. At its core, Joshua Oppenheimer’s documentary is about trauma, but it inverts the usual traumatic testimony. Instead of giving the survivors a voice, this piece gives it to the perpetrators who killed an estimated 1 million people in Indonesia suspected for being Communists, their sympathizers, Chinese people, or Christian.

These men recount their experiences in committing this genocide, and almost none of them show remorse or other emotional disturbance for what they did. They re-enact their experiences through both simple and elaborate stagings. In a simple one, the perpetrator shows how to garrote someone efficiently without as much blood loss as other execution methods. More complex stagings use costumes, sets, and even extras in supporting roles. The perpetrators re-enact these scenes with relish, while some of the extras appear frightened to be there.

Some critics question the decision of giving these perpetrators a voice about this situation and in this documentary. Documentary ethos is strongly tied with giving voice to those who would not have it otherwise, and yet The Act of Killing gives voice to those who already retain power. Had this documentary used talking heads to explain what happened and why, the results would have been … … I can’t find a word here.

But understanding the mind of the perpetrator is just as important as understanding the experiences of the survivor, if anything to prevent these atrocities from happening again. Oppenheimer’s use of the re-enactments provides a necessary layer of intervention, which renders their acts both watchable and ridiculous at the same time. The excess of their fun in remaking the scenes shows both their humanity and their forgetting of others’ humanity. These events seem fantasy to them, not reality, but to others watching those supposed fantasies it is a horrifying reality. And that reality needs to represented.